Projectile with aft-mounted cutting edges

ABSTRACT

A projectile includes an elongated shaft having a fore-end and an aft-end. A nose portion is affixed to the fore-end of the shaft, and cutting edges are attached near the aft-end of the shaft. For the present invention, the nose portion of the projectile is preferably made of a material having a greater density than the material that is used to construct the shaft of the projectile. In any event, the structure and configuration of the projectile is such that its center of gravity is located in the forward half of the projectile. Also, the cutting edges at the aft-end of the shaft can be configured to function as stabilizing fins for the projectile in flight.

FIELD OF THE INVENTION

The present invention pertains generally to projectiles. More particularly, the present invention pertains to projectiles that are suited for use with man-powered weapons, such as a crossbow. The present invention is particularly, but not exclusively, useful as a projectile having a center of gravity located towards the forward end of the projectile and having cutting edges mounted towards the rear of the projectile.

BACKGROUND OF THE INVENTION

Two of the most important considerations in the design and manufacture of projectiles are accuracy and effectiveness. In particular, these considerations may have greater importance when the projectile is to be fired from a so-called “man-powered” weapon, such as a crossbow or a compound bow. In general, projectiles that are used with such weapons will be constructed with an elongated shaft. Further, for hunting activities, these projectiles will typically employ a broadhead (cutting element) that is mounted at the fore-end of the shaft, and they will have some type of fletching (stabilizing element) that is mounted at the aft-end of the shaft. Both of these additions onto the shaft of a projectile (i.e. the cutting and stabilizing elements) can, however, have a profound effect on both the accuracy and the effectiveness of the projectile.

Insofar as accuracy is concerned, the in-flight stability of the projectile is critical. On this point, it is well known that stabilizing elements are most effectively located aft of the center of gravity, or center of pressure, of the projectile. Increased stability, of course, contributes to overall accuracy. On the other hand, unwanted aerodynamic forces that may be generated forward of the center of gravity, such as by an imperfect broadhead, may have substantial adverse effects on both the stability and accuracy of the projectile.

As for the effectiveness of a projectile, it is crucial that the projectile be accurately propelled. Further, it is important that the projectile have sufficient penetrating power upon contact with a target. With this in mind, it is recognized that establishing a relatively high momentum for the projectile (mass and velocity) at the time of its impact with the target is very desirable.

The result to be attained here is that the projectile needs to achieve an optimal penetration into the target. Of particular importance is that the cutting element of the projectile effectively penetrates the target.

In light of the above, it is an object of the present invention to provide a projectile that is predictably accurate. Another object of the present invention is to provide a projectile having enough momentum to be especially effective for hunting large game animals. Yet another object of the present invention is to provide a projectile that is easy to use, is relatively simple to manufacture, and is relatively cost effective.

SUMMARY OF THE INVENTION

In accordance with the present invention, a projectile is provided having an elongated shaft with a center of gravity that is located axially in the forward half of the projectile. Specifically, the location of the center of gravity in the forward end of the projectile is established in either of two ways. For one, two materials having different densities may be used for the structure of the projectile. For another, a single-type material can be configured to locate the center of gravity in the front quarter of the projectile. In either case, an array of cutting edges is mounted onto the shaft at the rear portion of the projectile.

When two materials are used for manufacture of the projectile, a nose portion consisting primarily of heavier, denser material is affixed to the forward end of the shaft. At the same time, a lighter, less dense material is used to manufacture the rest of the shaft. Thus, the projectile has more mass concentrated toward its forward half. Furthermore, the nose portion is aerodynamically clean; meaning the effects of aerodynamic forces on the nose portion during flight are minimized. For this purpose, the outer surface of the nose portion may be any of various geometrical shapes, such as ellipsoidal, cylindrical, or spherical. In any event, it is important that the center of gravity be located ahead of the midpoint, and preferably in the forward quarter of the projectile.

When the projectile of the present invention is manufactured using a single-type material, the projectile can be configured to locate its center of gravity ahead of the midpoint. To accomplish this, the projectile is constructed with the bulk of its material in its forward half. Stated differently, the mass of the projectile is not distributed equally along the length of the shaft.

In addition to the location of the center of gravity, the location of the cutting edges is an important aspect of the present invention. Structurally, an array of cutting edges is mounted on the projectile at the aft-end of the elongated shaft. In a preferred embodiment, the cutting edges will be configured to also function as stabilizing fins for the projectile, and three or more cutting edges will be used. More specifically, each cutting edge is preferably triangular in shape and the vertices of the cutting edge are coplanar with the shaft axis of the projectile. Also, in a preferred embodiment the cutting edge will be inclined in a rearward manner relative to the axis of the shaft.

Certain structural features of the present invention make it particularly suited for use with a man-powered weapon such as a crossbow. One such feature is the shape of the projectile that allows it to interact with the launch rail of a crossbow. For this purpose, the projectile is formed with two contact points; one contact point being near the fore-end of the shaft and one being near the aft-end of the shaft. At its aft-end, the shaft of the projectile is outwardly flared in a radial direction away from the shaft to create a substantially circular cross-section having a diameter “D_(max).” Thus, the contact point near the aft-end is established. This diameter, D_(max), at the aft-end of the shaft is substantially the same as the maximum diameter of the nose portion. Consequently, contact points at the fore-end and aft-end of the shaft will maintain the axis of the projectile shaft substantially parallel to the launcher rail of the crossbow.

Other features suited for use with a man-powered weapon include a nock and threaded receptacle that are located at the aft-end of the shaft. In detail, the nock is aligned perpendicularly to the shaft and is formed to engage with a bow string of a man-powered weapon such as a crossbow. On the other hand, the threaded receptacle extends from the aft-end of the shaft forwardly along the axis and into the shaft.

As envisioned for the present invention, when a projectile strikes a target, the projectile may become embedded in the target. Thus, a tool is provided that can engage with the threaded receptacle to more easily retrieve the projectile. More specifically, the tool for this purpose will be constructed with complementary threading designed for use with the threaded receptacle of the projectile.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:

FIG. 1 is a perspective view of a projectile for the present invention;

FIG. 2 is an exploded, cross-sectional view of the projectile as seen along line 2-2 in FIG. 1; and

FIG. 3 is a representative comparison of penetration depths for a projectile having forward mounted cutting edges, and for a projectile of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, a projectile as envisioned for the present invention is shown and is generally designated 10. As shown, the projectile 10 includes an elongated shaft 12 having a fore-end 14 and an aft-end 16. In FIG. 1, the elongated shaft 12 has a length (L_(a)) and defines an axis 18. Also as shown in FIG. 1, a nose portion 20 having a length (L_(a)) is affixed to the fore-end 14 of the elongated shaft 12, and is aligned along the axis 18. Also shown in FIG. 1, three cutting edges 22 a-c are attached to the aft-end 16 of the elongated shaft 12. The use of three cutting edges 22 a-c is exemplary, as more or fewer cutting edges 22 may be used.

Still referring to FIG. 1, the elongated shaft 12 is made of a material having a mass per unit length (m₁) and the nose portion 20 is made of a material having a different mass per unit length (m₂). As envisioned for the present invention, m₂>m₁. Consequently, the center of gravity 24 of the projectile 10 is located on the axis 18 at a distance more than ½(L_(n)+L_(s)) from the aft-end 16 of the elongated shaft 12. In FIG. 1, an exemplary location of the center of gravity 24 is shown. Typical materials used for the elongated shaft 12 (m₁) include, but are not limited to, aluminum, magnesium, beryllium, carbon fibers, and fiberglass. And, the material used for the nose portion 20 (m₂) is selected from a group comprising brass, bronze, stainless steel, tungsten, and depleted uranium. In an alternate embodiment, the elongated shaft 12 and the nose portion 20 are constructed using the same material. When the same material is used, due to a predetermined configuration of the projectile 10, the center of gravity 24 can still be located close to the fore-end 14 of the elongated shaft 12.

Next, referring to FIG. 2, a preferred embodiment of the projectile 10 is shown. As shown in FIG. 2, the nose portion 20 is comprised of two separate components: a nose cone 26 and a nose portion assembly 28. In further detail, the nose cone 26 comprises a connector rod 30 having a shoulder 32. An additional shoulder 33 is located on the fore-end 14 of the elongated shaft 12. Each shoulder 32, 33 connects to a corresponding receptacle 34, 35 located on opposite ends of the nose portion assembly 28. To attach the nose portion 20 to the projectile 10, the connector rod 30 will pass through an assembly channel 36 that extends through the nose portion assembly 28. After passing through the nose portion assembly 28, the connector rod 30 enters a connecting socket 38 formed within the fore-end 14 of the elongated shaft 12. As depicted in FIG. 2, the connector rod 30 and the connecting socket 38 are constructed with complementary threading 40 a-b to facilitate a secure connection. In addition, the nose cone 26 will have an outer surface that is selected from a group comprising ellipsoidal, cylindrical, and spherical shapes.

Still referring to FIG. 2, it can be seen how the cutting edges 22 a-b project outwardly in a radial direction from the axis 18 of the elongated shaft 12. Specifically, an obtuse angle “Θ” is formed as measured from the elongated shaft 12 to the cutting edge 22 a. In this configuration, the cutting edges 22 a-b may also serve as stabilizing fins for the projectile 10. In addition, FIG. 2 illustrates the locations of maximum diameters (D_(max)) of the projectile 10. As shown, the nose portion 20 has a maximum diameter (D_(max)) located at the nose portion assembly 28. Similarly, the aft-end 16 of the elongated shaft 12 is flared outwardly in a radial direction from the axis 18 to establish a maximum diameter (D_(max)) that is substantially the same as the maximum diameter of the nose portion 20.

FIG. 2 also illustrates components that are not easily visible in FIG. 1. First, a nock 42 is located at the aft-end 16 of the elongated shaft 12 and is configured to engage the bowstring of a man-powered weapon like a crossbow. In addition, a threaded receptacle 44 is provided. As illustrated in FIG. 2, the threaded receptacle 44 is aligned in the direction of the axis 18 defined by the elongated shaft 12. Furthermore, the threaded receptacle 44 extends into the elongated shaft 12. A tool (not shown) can be manufactured for use with the threaded receptacle 44 to facilitate retrieval of the projectile 10 when it becomes embedded in a target.

For discussion purposes, FIG. 3 illustrates a comparison of penetration depth for a conventional projectile 46 with fore-mounted cutting edges 48 and the projectile 10 of the present invention. As measured from a target face 50, the penetration depth 52 of the projectile 10 of the present invention is greater than the penetration depth 54 of the conventional projectile 46. As shown, the penetration depth 52, 54 is measured from the target face 50 to the cutting edge 22, 48 of the respective projectile 10, 46.

While the Projectile with Aft-Mounted Cutting Edges as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims. 

What is claimed is:
 1. A projectile which comprises: an elongated shaft defining an axis and having a fore-end and an aft-end, wherein the shaft has a length (L_(s)) and is made of a material having a first mass per unit length (m₁); a nose portion affixed to the fore-end of the shaft, wherein the nose portion has a length (L_(n)) and is made of a material having a second mass per unit length (m₂), wherein m₂ is greater than m₁ (m₂>m₁), with a consequent center of gravity for the projectile located substantially on the axis at a distance more than ½(L_(n)+L_(s)) from the aft-end of the shaft; and at least one cutting edge attached to the shaft and projecting outwardly in a radial direction from the axis.
 2. A projectile as recited in claim 1 wherein the nose portion has an outer surface formed with a shape selected from a group comprising ellipsoidal, cylindrical and spherical.
 3. A projectile as recited in claim 1 further comprising a plurality of stabilizing fins mounted adjacent the aft-end of the shaft.
 4. A projectile as recited in claim 3 wherein at least one stabilizing fin is formed with a cutting edge.
 5. A projectile as recited in claim 1 wherein the aft-end of the shaft is flared outwardly in a radial direction from the axis to establish a circular cross-section with a maximum diameter (D_(max)), and wherein the nose portion is formed to have a circular cross-section with a substantially same maximum diameter (D_(max)).
 6. A projectile as recited in claim 1 wherein the m₁ material is selected from a group comprising aluminum, magnesium, beryllium, carbon fibers, and fiber glass.
 7. A projectile as recited in claim 1 wherein the m₂ material is selected from a group comprising brass, bronze, stainless steel, tungsten and depleted uraniuim.
 8. A projectile as recited in claim 1 wherein the aft-end of the shaft is formed with a nock and a threaded receptacle, wherein the threaded receptacle is axially aligned and extends forward from the aft-end of the shaft to receive a tool therein for engagement therewith for retrieval of the projectile from a target.
 9. A projectile which comprises: an extended shaft of length “L” having a fore-end and an aft-end, wherein the extended shaft defines an axis and has a mass distribution with a center of gravity located substantially on the axis within a distance of ½L from the fore-end of the extended shaft; and a plurality of cutting edges attached to the extended shaft adjacent the aft-end thereof and projecting outwardly in a radial distance from the axis.
 10. A projectile as recited in claim 9 wherein the extended shaft comprises: a shaft portion having a length (L_(s)), wherein the shaft portion is made of a material having a first mass per unit length (m₁); and a nose portion formed at the fore-end of the extended shaft, wherein the nose portion has a length (L_(n)) and is made of a material having a second mass per unit length (m₂), wherein m₂ is greater than m₁, L=L_(s)+L_(n), and wherein L_(n) is less than 0.5L with a consequent center of gravity for the projectile located substantially on the axis at a distance more than ½(L_(n)+L_(s)) from the aft-end of the shaft.
 11. A projectile as recited in claim 10 wherein the nose portion has an outer surface formed with a shape selected from a group comprising ellipsoidal, cylindrical and spherical.
 12. A projectile as recited in claim 10 further comprising a plurality of stabilizing fins mounted adjacent the aft-end of the shaft portion.
 13. A projectile as recited in claim 12 wherein at least one stabilizing fin is formed with a cutting edge.
 14. A projectile as recited in claim 10 wherein the aft-end of the extended shaft is flared outwardly in a radial direction from the axis to establish a circular cross-section with a maximum diameter (D_(max)), and wherein the nose portion is formed to have a circular cross-section with a substantially same maximum diameter (D_(max)).
 15. A projectile as recited in claim 10 wherein the m₁ material is selected from a group comprising aluminum, magnesium, beryllium, carbon fibers, and fiber glass.
 16. A projectile as recited in claim 10 wherein the m₂ material is selected from a group comprising brass, bronze, stainless steel, tungsten and depleted uranium.
 17. A method for manufacturing a projectile which comprises the steps of: providing an elongated shaft defining an axis and having a fore-end and an aft-end, wherein the shaft has a length (L_(s)) and is made of a material having a first mass per unit length (m₁); affixing a nose portion to the fore-end of the shaft, wherein the nose portion has a length (L_(n)) and is made of a material having a second mass per unit length (m₂), wherein m₂ is greater than m₁ (m₂>m₁), with a consequent center of gravity for the projectile located substantially on the axis at a distance more than ½(L_(n)+L_(s)) from the aft-end of the shaft; and attaching at least one cutting edge to the shaft to project outwardly in a radial direction from the axis.
 18. A method as recited in claim 17 wherein the attaching step comprises the steps of: mounting a plurality of stabilizing fins adjacent the aft-end of the shaft; and forming at least one stabilizing fin with a cutting edge.
 19. A method as recited in claim 17 further comprising the steps of: flaring the aft-end of the shaft outwardly in a radial direction from the axis to establish a circular cross-section with a maximum diameter (D_(max)); and forming the nose portion to have a circular cross-section with a substantially same maximum diameter (D_(max)).
 20. A method as recited in claim 17 further comprising the steps of: selecting the m₁ material from a group comprising aluminum, magnesium, beryllium, carbon fibers, and fiber glass; and selecting the m₂ material from a group comprising brass, bronze, stainless steel, tungsten and depleted uraniuim. 